Efficacy of IP-10 as a biomarker for the diagnosis of tuberculosis

Abstract

Background: The aim of this study was to evaluate inducible protein 10 (IP-10) as an additional biomarker for specific tuberculosis (TB) infection in an area of intermediate TB burden and to evaluate the ability of IP-10 to distinguish between active TB and latent TB infection (LTBI).Method: Eighty individuals were prospectively enrolled: 25 with active pulmonary TB, 25 household contacts, and 30 healthy controls. We measured IP-10 in serum and in supernatants from whole blood stimulated with Mycobacterium tuberculosis-specific antigen. Enrolled individuals were also tested using a QuantiFERON-TB Gold In-Tube assay (QFT-GIT) and a tuberculin skin test.Results: TB antigen-dependent IP-10 secretion (IP-10 TB-Nil) was significantly increased in the active TB and LTBI groups compared with controls, but did not differ significantly between the active TB and the LTBI groups. Serum IP-10 levels were higher in the active TB group (174.9 pg/ml) than in the LTBI group (102.7 pg/ml, P=0.002). When the IP-10 response to TB antigen was scored based on receiver operating characteristic analysis, active TB was predicted with 88% sensitivity and 90.5% specificity. The QFT-GIT assay showed 96% sensitivity and 81% specificity for active TB. The combination of the TB antigen-dependent IP-10 response and serum IP-10 level resulted in 81.6% correct classification of active TB or LTBI.Conclusion: The IP-10 response to TB antigen stimulation may represent a specific biomarker for TB infection, but does not by itself distinguish between active TB and LTBI. Serum IP-10 may help to distinguish active TB from LTBI when used in combination with another marker.